三维四向编织陶瓷基复合材料改进模型及刚度预报

基于对三维四向编织陶瓷基复合材料CT扫描结果的观察和理论分析, 参考现有交织模型, 建立了改进的胞元三维实体模型, 较为真实地反映了材料内部的细观结构。模型内部纤维束横截面沿纤维束轴向不断发生形状和面积的周期性变化, 纤维束横截面呈平行四边形、五边形交替变化, 不同纤维束轴线间呈交织关系, 接近材料内部纤维束间打紧后的挤压变形规律。通过测算平均纱线填充因子并配合有限元法获得了纤维束及材料的弹性性能, 与试验结果符合较好。有限元仿真显示在材料单胞内, 纤维束承担主要载荷, 纤维束与基体的某些交界处往往会出现应力集中现象, 可能是发生裂纹扩展及局部破坏的主要区域。该细观应力场的获得也为分析材料破坏机理和强度提供了基础。 

Improved model and stiffness prediction of 3D four-directional braided ceramic-matrix composites

Based on the CT scan results of 3D four-directional braided ceramic-matrix composites and theoretical analysis,referred to the existing interlaced model,an improved 3D cell element model was established.This model truly reflects the mesoscopic structure of the internal material.The yarns’cross-section along their axes model var-ied cyclically in shape and area,yarn’s cross-sections alternate transformed form parallelograms to pentagons,each yarn’s axis presented interlaced relationships,close to the extrusion deformation law of tight yarns in materials.By measuring the average yarn packing factor and using the finite element method,the elastic properties of yarns and materials were obtained.The predicted value agrees well with the test data.The finite element simulation reveals that the yarns undertake the main load in the materials’cell model.Some of the yarns and matrixes interfaces tend to appear stress concentration phenomenon.These areas could mostly produce crack propagations and local dama-ges.The determination of the mesoscopic stress field also provides a foundation for the analysis of failure mechanism and the strength of the materials.